U.S. patent number 7,833,666 [Application Number 11/780,416] was granted by the patent office on 2010-11-16 for electric current-producing device having sulfone-based electrolyte.
This patent grant is currently assigned to Arizona Board of Regents for and behalf of Arizona State University. Invention is credited to Charles Austen Angell, Xiao-Guang Sun.
United States Patent |
7,833,666 |
Angell , et al. |
November 16, 2010 |
**Please see images for:
( Certificate of Correction ) ** |
Electric current-producing device having sulfone-based
electrolyte
Abstract
Electrolytic solvents and applications of such solvents
including electric current-producing devices. For example, a
solvent can include a sulfone compound of R1--SO2--R2, with R1
being an alkyl group and R2 a partially oxygenated alkyl group, to
exhibit high chemical and thermal stability and high oxidation
resistance. For another example, a battery can include, between an
anode and a cathode, an electrolyte which includes ionic
electrolyte salts and a non-aqueous electrolyte solvent which
includes a non-symmetrical, non-cyclic sulfone. The sulfone has a
formula of R1--SO2--R2, wherein R1 is a linear or branched alkyl or
partially or fully fluorinated linear or branched alkyl group
having 1 to 7 carbon atoms, and R2 is a linear or branched or
partially or fully fluorinated linear or branched oxygen containing
alkyl group having 1 to 7 carbon atoms. The electrolyte can include
an electrolyte co-solvent and an electrolyte additive for
protective layer formation.
Inventors: |
Angell; Charles Austen (Mesa,
AZ), Sun; Xiao-Guang (Tempe, AZ) |
Assignee: |
Arizona Board of Regents for and
behalf of Arizona State University (Scottsdale, AZ)
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Family
ID: |
36692894 |
Appl.
No.: |
11/780,416 |
Filed: |
July 19, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070298326 A1 |
Dec 27, 2007 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/US2006/001975 |
Jan 19, 2006 |
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60645536 |
Jan 19, 2005 |
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Current U.S.
Class: |
429/340; 568/35;
429/341; 429/321; 429/324; 568/32 |
Current CPC
Class: |
H01M
6/164 (20130101); H01G 11/60 (20130101); H01M
10/0569 (20130101); H01G 9/038 (20130101); H01M
6/168 (20130101); H01G 11/64 (20130101); H01M
10/0567 (20130101); H01M 10/052 (20130101); Y02E
60/10 (20130101); H01M 2300/0025 (20130101); H01M
2300/0037 (20130101); Y02E 60/13 (20130101) |
Current International
Class: |
H01M
6/16 (20060101); H01M 10/0569 (20060101) |
References Cited
[Referenced By]
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2516920 |
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May 1983 |
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FR |
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GB |
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Jun 1997 |
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JP |
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Aug 2006 |
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JP |
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Sep 2006 |
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JP |
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Jan 2007 |
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JP |
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WO |
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WO |
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WO |
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Apr 2009 |
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WO |
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Primary Examiner: Walker; Keith
Attorney, Agent or Firm: Fish & Richardson P.C.
Government Interests
STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH OR DEVELOPMENT
The U.S. Government has a paid-up license in the present invention
and the right in limited circumstances to require the patent owner
to license others on fair and reasonable terms as provided by the
terms of Grant No. DEFG039ER14378-003 and DEFG03945541 awarded by
the U.S. Department of Energy.
Parent Case Text
PRIORITY CLAIMS
The present non-provisional patent application is, under 35 U.S.C.
.sctn.120, a continuing patent application of and claims priority
to a co-pending PCT Application No. PCT/US2006/001975 entitled
"ELECTRIC CURRENT-PRODUCING DEVICE HAVING SULFONE-BASED
ELECTROLYTE" and filed on Jan. 19, 2006 (PCT Publication No.
WO2006078866(A2)) which, under 35 U.S.C. .sctn.119(e)(1), claims
priority to a U.S. provisional application Ser. No. 60/645,536
entitled "New Sulfone Electrolytes for Rechargeable Lithium
Batteries" and filed on Jan. 19, 2005 by Xiao-Guang Sun et al.
The above referenced prior patent applications are incorporated by
reference in their entirety as part of the specification of the
present application.
Claims
What is claimed is:
1. An electrolyte element for use in an electric current-producing
device, comprising: one or more ionic electrolyte salts; and a
non-aqueous electrolyte solvent including one or more
non-symmetrical, non-cyclic sulfones of the general formula:
R1--SO2--R2, wherein the R1 group is a linear or branched alkyl or
partially or fully fluorinated linear or branched alkyl group
having 1 to 7 carbon atoms, and the R2 group, which is different in
formulation than the R1 group, is a linear or branched or partially
or fully fluorinated linear or branched oxygen containing alkyl
group having 1 to 7 carbon atoms.
2. The electrolyte element of claim 1, wherein the R1 group
comprises at least one of: methyl (--CH.sub.3); ethyl
(--CH.sub.2CH.sub.3); n-propyl (--CH.sub.2CH.sub.2CH.sub.3);
n-butyl (--CH.sub.2CH.sub.2CH.sub.2CH.sub.3); n pentyl
(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3); n-hexyl
(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3); n-heptyl
(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3);
iso-propyl (--CH(CH.sub.3).sub.2); iso-butyl
(--CH.sub.2CH(CH.sub.3).sub.2); sec-butyl
(--CH(CH.sub.3)CH.sub.2CH.sub.3); tert-butyl (--C(CH.sub.3).sub.3);
iso-pentyl (--CH.sub.2CH.sub.2CH(CH.sub.3).sub.2); trifluoromethyl
(--CF.sub.3);2,2,2-trifluoroethyl
(--CH.sub.2CF.sub.3);1,1-difluoroethyl (--CF.sub.2CH.sub.3);
perfluoroethyl (--CF.sub.2CF.sub.3); 3,3,3-trifluoro-n-propyl
(--CH.sub.2CH.sub.2CF.sub.3);2,2-difluoro-npropyl
(--CH.sub.2CF.sub.2 CH.sub.3);1,1-difluoro-n-propyl (--CF.sub.2
CH.sub.2 CH.sub.3);1,1,3,3,3-pentafluoro-n-propyl (--CF.sub.2
CH.sub.2 CF.sub.3);2,2,3,3,3-pentafluoro-n-propyl
(--CH.sub.2CF.sub.2CF.sub.3); perfluoro-n-propyl
(--CF.sub.2CF.sub.2CF.sub.3); perfluoro-n-butyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.3); perfluoro-npentyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3); perfluoro-n-hexyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3);
perfluoro-n-heptyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3);--CF(CH.sub.-
3).sub.2;--CH(CH.sub.3)CF.sub.3;--CF(CF.sub.3).sub.2;--CH(CF.sub.3).sub.2;
--CH.sub.2CF(CH.sub.3).sub.2;--CF.sub.2CH(CH.sub.3).sub.2;--CH.sub.2CH(CH-
.sub.3)CF.sub.3;--CH.sub.2CH(CF.sub.3).sub.2;--CF.sub.2CF(CF.sub.3).sub.2;-
--C(CF.sub.3).sub.3.
3. The electrolyte element of claim 1, wherein the R2 group
comprises at least one of
--CH.sub.2OCH.sub.3;--CF.sub.2OCH.sub.3;--CF.sub.2OCF.sub.3;--CH.sub.2CH.-
sub.2OCH.sub.3;--CH.sub.2CF.sub.2OCH.sub.3;--CF.sub.2CH.sub.2OCH.sub.3;
--CF.sub.2CF.sub.2OCH.sub.3;--CF.sub.2CF.sub.2OCF.sub.3;
--CF.sub.2CH.sub.2OCF.sub.3;--CH.sub.2CF.sub.2OCF.sub.3;--CH.sub.2CH.sub.-
2OCF.sub.3;
--CHFCF.sub.2OCF.sub.2H;--CF.sub.2CF.sub.2OCF(CF.sub.3).sub.2;--CF.sub.2C-
H.sub.2OCF(CF.sub.3).sub.2;--CH.sub.2CF.sub.2OCF(CF.sub.3).sub.2;
--CH.sub.2CH.sub.2OCF(CF.sub.3).sub.2;--CF.sub.2CF.sub.2OC(CF.sub.3).sub.-
3;--CF.sub.2CH.sub.2OC(CF.sub.3).sub.3;--CH.sub.2CF.sub.2OC(CF.sub.3)
.sub.3;
--CH.sub.2CH.sub.2OC(CF.sub.3).sub.3;--CH.sub.2CH.sub.2OCH.sub.2C-
H.sub.3;--CH.sub.2CH.sub.2OCH.sub.2CF.sub.3;--CH.sub.2CH.sub.2OCF.sub.2CH.-
sub.3;
--CH.sub.2CH.sub.2OCF.sub.2CF.sub.3;--CH.sub.2CF.sub.2OCH.sub.2CH.s-
ub.3;--CH.sub.2CF.sub.2OCF.sub.2CH.sub.3;--CH.sub.2CF.sub.2OCH.sub.2CF.sub-
.3;
--CH.sub.2CF.sub.2OCF.sub.2CF.sub.3;--CF.sub.2CH.sub.2OCH.sub.2CH.sub.-
3;--CF.sub.2CH.sub.2OCF.sub.2CH.sub.3;--CF.sub.2CH.sub.2OCH.sub.2CF.sub.3;
--CF.sub.2CH.sub.2OCF.sub.2CF.sub.3;--CF.sub.2CF.sub.2OCH.sub.2CH.sub.3;--
-CF.sub.2CF.sub.2OCF.sub.2CH.sub.3;--CF.sub.2CF.sub.2OCH.sub.2CF.sub.3;
--CF.sub.2CF.sub.2OCF.sub.2CF.sub.3;--CF.sub.2CF.sub.2CF.sub.2OCH.sub.3;--
-CF.sub.2CF.sub.2CH.sub.2OCH.sub.3;--CF.sub.2CH.sub.2CF.sub.2OCH.sub.3;
--CH.sub.2CF.sub.2CF.sub.2OCH.sub.3;--CH.sub.2CF.sub.2CH.sub.2OCH.sub.3;--
-CH.sub.2CH.sub.2CF.sub.2OCH.sub.3;--CF.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;--CF.sub.2CF.sub.2CF.sub.2OCF.sub.3;--
-CF.sub.2CF.sub.2CH.sub.2OCF.sub.3;--CF.sub.2CH.sub.2CF.sub.2OCF.sub.3;
--CH.sub.2CF.sub.2CF.sub.2OCF.sub.3;--CH.sub.2CH.sub.2CF.sub.2OCF.sub.3;--
-CH.sub.2CF.sub.2CH.sub.2OCF.sub.3;
--CF.sub.2CH.sub.2CH.sub.2OCF.sub.3;
--CH.sub.2CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;--CH.sub.2CH.sub.2CH.sub.2CH.-
sub.2CH.sub.2OCH.sub.3;--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2O-
CH.sub.3;
--CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.3;--CH.sub.2CH.sub.2O-
CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.3.
4. The electrolyte element of claim 1, wherein the ionic
electrolyte salt comprises at least one of MClO.sub.4, MPF.sub.6,
MPF.sub.X(C.sub.nF.sub.2n+1).sub.6-X, MBF.sub.4,
MBF.sub.4-x(C.sub.nF.sub.2n+1).sub.X, MAsF.sub.6, MSCN,
MB(CO.sub.2).sub.4, MN(SO.sub.2CF.sub.3).sub.2, and
MSO.sub.3CF.sub.3, where "M" is lithium or sodium, or any mixture
thereof.
5. The electrolyte element of claim 1, comprising an electrolyte
co-solvent.
6. The electrolyte element of claim 5, wherein the electrolyte
co-solvent comprises at least one of co-solvents including
carbonates, N-methyl acetamide, acetonitrile, symmetric sulfones,
sulfolanes, 1,3-dioxolanes, glymes, polyethylene glycols,
siloxanes, and ethylene oxide grafted siloxanes.
7. The electrolyte element of claim 1, comprising an electrolyte
additive.
8. The electrolyte element of claim 7, wherein the electrolyte
additive comprises at least one of: vinylene carbonate (VC),
ethylene sulfite (ES), propylene sulfite (PS), fluoroethylene
sulfite (FEC), .alpha.-bromo-.gamma.-butyrolactone, methyl
chloroformate, t-butylene carbonate, 12-crown-4, carbon dioxide
(CO.sub.2), sulfur dioxide (SO.sub.2), sulfur trioxide (SO.sub.3),
acid anhydrides, reaction products of carbon disulfide and lithium,
polysulfide, and other inorganic additives.
9. An electric current-producing device, comprising: a cathode; an
anode; and a non-aqueous electrolyte element disposed between the
cathode and anode, the non-aqueous electrolyte element including an
electrolyte salt and a non-symmetrical, noncyclic sulfone of the
general formula: R1--SO2--R2, wherein R1 is an alkyl group, and R2
is an alkyl group including oxygen.
10. The electric current-producing device of claim 9, wherein the
device is a voltaic cell.
11. The electric current-producing device of claim 9, wherein the
device is a supercapacitor.
12. The electric current-producing device of claim 9, wherein the
alkyl group of R1 includes oxygen and has a different formulation
than R2.
13. The electric current-producing device of claim 12, wherein the
R1 or R2 group comprises at least one of:
--CH.sub.2OCH.sub.3;--CF.sub.2OCH.sub.3;--CF.sub.2OCF.sub.3;--CH.sub.2CH.-
sub.2OCH.sub.3;--CH.sub.2CF.sub.2OCH.sub.3;
--CF.sub.2CH.sub.2OCH.sub.3;--CF.sub.2CF.sub.2OCH.sub.3;--CF.sub.2CF.sub.-
2OCF.sub.3;--CF.sub.2CH.sub.2OCF.sub.3;--CH.sub.2CF.sub.2OCF.sub.3;--CH.su-
b.2CH.sub.2OCF.sub.3;
--CHFCF.sub.2OCF.sub.2H;--CF.sub.2CF.sub.2OCF(CF.sub.3).sub.2;--CF.sub.2C-
H.sub.2OCF(CF.sub.3).sub.2;--CH.sub.2CF.sub.2OCF(CF.sub.3).sub.2;
--CH.sub.2CH.sub.2OCF(CF.sub.3).sub.2;--CF.sub.2CF.sub.2OC(CF.sub.3).sub.-
3;--CF.sub.2CH.sub.2OC(CF.sub.3).sub.3;--CH.sub.2CF.sub.2OC(CF.sub.3).sub.-
3;
--CH.sub.2CH.sub.2OC(CF.sub.3).sub.3;--CH.sub.2CH.sub.2OCH.sub.2CH.sub.-
3;--CH.sub.2CH.sub.2OCH.sub.2CF.sub.3;--CH.sub.2CH.sub.2OCF.sub.2CH.sub.3;
--CH.sub.2CH.sub.2OCF.sub.2CF.sub.3;--CH.sub.2CF.sub.2OCH.sub.2CH.sub.3;--
-CH.sub.2CF.sub.2OCF.sub.2CH.sub.3;--CH.sub.2CF.sub.2OCH.sub.2CF.sub.3;
--CH.sub.2CF.sub.2OCF.sub.2CF.sub.3;--CF.sub.2CH.sub.2OCH.sub.2CH.sub.3;--
-CF.sub.2CH.sub.2OCF.sub.2CH.sub.3;--CF.sub.2CH.sub.2OCH.sub.2CF.sub.3;
--CF.sub.2CH.sub.2OCF.sub.2CF.sub.3;--CF.sub.2CF.sub.2OCH.sub.2CH.sub.3;--
-CF.sub.2CF.sub.2OCF.sub.2CH.sub.3;--CF.sub.2CF.sub.2OCH.sub.2CF.sub.3;
--CF.sub.2CF.sub.2OCF.sub.2CF.sub.3;--CF.sub.2CF.sub.2CF.sub.2OCH.sub.3;--
-CF.sub.2CF.sub.2CH.sub.2OCH.sub.3;--CF.sub.2CH.sub.2CF.sub.2OCH.sub.3;
--CH.sub.2CF.sub.2CF.sub.2OCH.sub.3;--CH.sub.2CF.sub.2CH.sub.2OCH.sub.3;--
-CH.sub.2CH.sub.2CF.sub.2OCH.sub.3;--CF.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;--CF.sub.2CF.sub.2CF.sub.2OCF.sub.3;--
-CF.sub.2CF.sub.2CH.sub.2OCF.sub.3;--CF.sub.2CH.sub.2CF.sub.2OCF.sub.3;
--CH.sub.2CF.sub.2CF.sub.2OCF.sub.3;--CH.sub.2CH.sub.2CF.sub.2OCF.sub.3;--
-CH.sub.2CF.sub.2CH.sub.2OCF.sub.3;--CF.sub.2CH.sub.2CH.sub.2OCF.sub.3;
--CH.sub.2CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;--CH.sub.2CH.sub.2CH.sub.2CH.-
sub.2CH.sub.2
OCH.sub.3;--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2
OCH.sub.3; --CH.sub.2CH.sub.2 OCH.sub.2CH.sub.2
OCH.sub.3;--CH.sub.2CH.sub.2 OCH.sub.2CH.sub.2 OCH.sub.2CH.sub.2
OCH.sub.3.
14. The electric current-producing device of claim 9, wherein the
R1 group comprises at least one of: methyl (--CH.sub.3); ethyl
(--CH.sub.2CH.sub.3); n-propyl (--CH.sub.2CH.sub.2CH.sub.3);
n-butyl (--CH.sub.2CH.sub.2CH.sub.2CH.sub.3); n-pentyl
(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3); n-hexyl
(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3); n-heptyl
(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3);
iso-propyl (--CH(CH.sub.3).sub.2); iso-butyl
(--CH.sub.2CH(CH.sub.3).sub.2); sec-butyl
(--CH(CH.sub.3)CH.sub.2CH.sub.3); tert-butyl (--C(CH.sub.3).sub.3);
iso-pentyl (--CH.sub.2CH.sub.2CH(CH.sub.3).sub.2); trifluoromethyl
(--CF.sub.3);2,2,2-trifluoroethyl
(--CH.sub.2CF.sub.3);1,1-difluoroethyl (--CF.sub.2CH.sub.3);
perfluoroethyl (--CF.sub.2CF.sub.3);3,3,3-trifluoro-n-propyl
(--CH.sub.2 CH.sub.2CF.sub.3);2,2-difluoro-n-propyl
(--CH.sub.2CF.sub.2CH.sub.3);1,1-difluoro-n-propyl
(--CF.sub.2CH.sub.2CH.sub.3);1,1,3,3,3-pentafluoro-n-propyl
(--CF.sub.2CH.sub.2CF.sub.3);2,2,3,3,3-pentafluoro-n-propyl
(--CH.sub.2CF.sub.2CF.sub.3); perfluoro-n-propyl
(--CF.sub.2CF.sub.2CF.sub.3); perfluoro-n-butyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.3); perfluoro-n-pentyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3); perfluoro-n-hexyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3);
perfluoro-n-heptyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3);--CF(CH.sub.-
3).sub.2;
--CH(CH.sub.3)CF.sub.3;--CF(CF.sub.3).sub.2;--CH(CF.sub.3).sub.2-
;--CH.sub.2CF(CH.sub.3).sub.2;--CF.sub.2CH(CH.sub.3).sub.2;--CH.sub.2CH(CH-
.sub.3)CF.sub.3;
--CH.sub.2CH(CF.sub.3).sub.2;--CF.sub.2CF(CF.sub.3).sub.2;--C(CF.sub.3).s-
ub.3.
15. The electric current-producing device of claim 9, wherein the
ionic electrolyte salt comprises at least one of MClO.sub.4,
MPF.sub.6, MPF.sub.X(C.sub.nF.sub.2n+).sub.6-X, MBF.sub.4,
MBF.sub.4-X(C.sub.nF.sub.2n+1).sub.X, MAsF.sub.6, MSCN,
MB(CO.sub.2).sub.4, MN(SO.sub.2CF.sub.3).sub.2, and
MSO.sub.3CF.sub.3, where "M" is lithium or sodium, or any mixture
thereof.
16. The electric current-producing device of claim 9, wherein the
electrolyte element includes an electrolyte co-solvent.
17. The electric current-producing device of claim 16, wherein the
electrolyte co-solvent comprises at least one of: co-solvents
including carbonates, N-methyl acetamide, acetonitrile, symmetric
sulfones, sulfolanes, 1,3-dioxolanes, glymes, polyethylene glycols,
siloxanes, and ethylene oxide grafted siloxanes.
18. The electric current-producing device of claim 9, wherein the
electrolyte element further includes an electrolyte additive, and
other inorganic additives.
19. The electric current-producing device of claim 18, wherein the
electrolyte additive comprises at least one of: vinylene carbonate
(VC), ethylene sulfite (ES), propylene sulfite (PS), fluoroethylene
sulfite (FEC), .alpha.-bromo-.gamma.-butyrolactone, methyl
chloroformate, t-butylene carbonate, 12-crown-4, carbon dioxide
(CO.sub.2), sulfur dioxide (SO.sub.2), sulfur trioxide (SO.sub.3),
acid anhydrides, reaction products of carbon disulfide and lithium,
polysulfide, and other inorganic additives.
20. An electrolyte for an electric current-producing device,
comprising a non-aqueous electrolyte solvent including an
non-symmetrical, non-cyclic sulfone of the general formula:
R1--SO2--R2, wherein R1 is an alkyl group, and R2 is an alkyl group
including oxygen.
21. The electrolyte of claim 20, wherein the alkyl group of R1
includes oxygen and has a different formulation than R2.
22. The electrolyte of claim 21, wherein the R1 or R2 group
comprises at least one of:
--CH.sub.2OCH.sub.3;--CF.sub.2OCH.sub.3;--CF.sub.2OCF.sub.3;--CH.sub.2CH.-
sub.2OCH.sub.3;
--CH.sub.2CF.sub.2OCH.sub.3;--CF.sub.2CH.sub.2OCH.sub.3;
--CF.sub.2CF.sub.2OCH.sub.3;--CF.sub.2CF.sub.2OCF.sub.3;--CF.sub.2CH.sub.-
2OCF.sub.3;--CH.sub.2CF.sub.2OCF.sub.3;--CH.sub.2CH.sub.2OCF.sub.3;
--CHFCF.sub.2OCF.sub.2H;--CF.sub.2CF.sub.2OCF(CF.sub.3).sub.2;--CF.sub.2C-
H.sub.2OCF(CF.sub.3).sub.2;--CH.sub.2CF.sub.2OCF(CF.sub.3).sub.2;
--CH.sub.2CH.sub.2OCF(CF.sub.3).sub.2;--CF.sub.2CF.sub.2OC(CF.sub.3).sub.-
3;
--CF.sub.2CH.sub.2OC(CF.sub.3).sub.3;--CH.sub.2CF.sub.2OC(CF.sub.3).sub-
.3;
--CH.sub.2CH.sub.2OC(CF.sub.3).sub.3;--CH.sub.2CH.sub.2OCH.sub.2CH.sub-
.3;--CH.sub.2CH.sub.2OCH.sub.2CF.sub.3;--CH.sub.2CH.sub.2OCF.sub.2CH.sub.3-
;
--CH.sub.2CH.sub.2OCF.sub.2CF.sub.3;--CH.sub.2CF.sub.2OCH.sub.2CH.sub.3;-
--CH.sub.2CF.sub.2OCF.sub.2CH.sub.3;--CH.sub.2CF.sub.2OCH.sub.2CF.sub.3;
--CH.sub.2CF.sub.2OCF.sub.2CF.sub.3;--CF.sub.2CH.sub.2OCH.sub.2CH.sub.3;--
-CF.sub.2CH.sub.2OCF.sub.2CH.sub.3;--CF.sub.2CH.sub.2OCH.sub.2CF.sub.3;
--CF.sub.2CH.sub.2OCF.sub.2CF.sub.3;--CF.sub.2CF.sub.2OCH.sub.2CH.sub.3;--
-CF.sub.2CF.sub.2OCF.sub.2CH.sub.3;--CF.sub.2CF.sub.2OCH.sub.2CF.sub.3;
--CF.sub.2CF.sub.2OCF.sub.2CF.sub.3;--CF.sub.2CF.sub.2CF.sub.2OCH.sub.3;--
-CF.sub.2CF.sub.2CH.sub.2OCH.sub.3;--CF.sub.2CH.sub.2CF.sub.2OCH.sub.3;
--CH.sub.2CF.sub.2CF.sub.2OCH.sub.3;--CH.sub.2CF.sub.2CH.sub.2OCH.sub.3;--
-CH.sub.2CH.sub.2CF.sub.2OCH.sub.3;--CF.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;--CF.sub.2CF.sub.2CF.sub.2OCF.sub.3;--
-CF.sub.2CF.sub.2CH.sub.2OCF.sub.3;--CF.sub.2CH.sub.2CF.sub.2OCF.sub.3;
--CH.sub.2CF.sub.2CF.sub.2OCF.sub.3;--CH.sub.2CH.sub.2CF.sub.2OCF.sub.3;--
-CH.sub.2CF.sub.2CH.sub.2OCF.sub.3;--CF.sub.2CH.sub.2CH.sub.2OCF.sub.3;
--CH.sub.2CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;--CH.sub.2CH.sub.2CH.sub.2CH.-
sub.2CH.sub.2OCH.sub.3;--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2O-
CH.sub.3;
--CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.3;--CH.sub.2CH.sub.2O-
CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.3 .
23. The electrolyte of claim 21, wherein the R1 group comprises at
least one of: methyl (--CH.sub.3); ethyl (--CH.sub.2CH.sub.3);
n-propyl (--CH.sub.2CH.sub.2CH.sub.3); n-butyl
(--CH.sub.2CH.sub.2CH.sub.2CH.sub.3); n-pentyl
(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3); n-hexyl
(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3); n-heptyl
(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3);
iso-propyl (--CH(CH.sub.3).sub.2); iso-butyl
(--CH.sub.2CH(CH.sub.3).sub.2); sec-butyl
(--CH(CH.sub.3)CH.sub.2CH.sub.3); tert-butyl (--C(CH.sub.3).sub.3);
iso-pentyl (--CH.sub.2CH.sub.2CH(CH.sub.3).sub.2); trifluoromethyl
(--CF.sub.3);2,2,2-trifluoroethyl
(--CH.sub.2CF.sub.3);1,1-difluoroethyl (--CF.sub.2 CH.sub.3);
perfluoroethyl (--CF.sub.2 CF.sub.3); 3,3,3-trifluoro-n-propyl
(--CH.sub.2CH.sub.2CF.sub.3);2,2-difluoro-n-propyl (--CH.sub.2
CF.sub.2 CH.sub.3);1,1-difluoro-n-propyl (--CF.sub.2 CH.sub.2
CH.sub.3);1,1,3,3,3-pentafluoro-n-propyl (--CF.sub.2 CH.sub.2
CF.sub.3);2,2,3,3,3-pentafluoro-n-propyl
(--CH.sub.2CF.sub.2CF.sub.3); perfluoro-n-propyl
(--CF.sub.2CF.sub.2CF.sub.3); perfluoro-n-butyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.3); perfluoro-n-pentyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3); perfluoro-n-hexyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3);
perfluoro-n-heptyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3);
--CF(CH.sub.3).sub.2;--CH(CH.sub.3)CF.sub.3;--CF(CF.sub.3).sub.2;
--CH(CF.sub.3).sub.2;--CH.sub.2CF(CH.sub.3).sub.2;--CF.sub.2CH(CH.sub.3).-
sub.2;--CH.sub.2CH(--CH.sub.3)CF.sub.3;--CH.sub.2CH(CF.sub.3).sub.2;--CF.s-
ub.2CF(CF.sub.3).sub.2; --C(CF.sub.3).sub.3.
24. The electrolyte of claim 20, wherein the ionic electrolyte salt
comprises at least one of MClO.sub.4, MPF.sub.6,
MPF.sub.X(C.sub.nF.sub.2n+1).sub.6-X, MBF.sub.4,
MBF.sub.4-X(C.sub.nF.sub.2n+1).sub.X, MAsF.sub.6, MSCN,
MB(CO.sub.2).sub.4, MN(SO.sub.2CF.sub.3).sub.2, and
MSO.sub.3CF.sub.3, where "M" is lithium or sodium, or any mixture
thereof.
25. The electrolyte of claim 21, further including an electrolyte
co-solvent.
26. The electrolyte of claim 25, wherein the electrolyte cosolvent
comprises at least one of co-solvents including carbonates,
N-methyl acetamide, acetonitrile, symmetric sulfones, sulfolanes,
1,3-dioxolanes, glymes, polyethylene glycols, siloxanes, and
ethylene oxide grafted siloxanes.
27. The electrolyte of claim 20, further including an electrolyte
additive.
28. The electrolyte of claim 27, wherein the electrolyte additive
comprises at least one of vinylene carbonate (VC), ethylene sulfite
(ES), propylene sulfite (PS), fluoroethylene sulfite (FEC),
.alpha.-bromo-.gamma.-butyrolactone, methyl chloroformate,
t-butylene carbonate,12-crown-4, carbon dioxide (CO.sub.2), sulfur
dioxide (SO.sub.2), sulfur trioxide (SO.sub.3), acid anhydrides,
reaction products of carbon disulfide and lithium, polysulfide, and
other inorganic additives.
29. A method of forming an electric current-producing device,
comprising: providing a cathode; providing an anode; and providing
a non-aqueous electrolyte element disposed between the cathode and
anode, the non-aqueous electrolyte element including an electrolyte
salt and a non-symmetrical, non-cyclic sulfone of the general
formula: R1--SO2--R2, wherein R1 is an alkyl group, and R2 is an
alkyl group including oxygen.
30. The method of claim 29, wherein the alkyl group of R1 includes
oxygen and has a different formulation than R2.
31. The method of claim 30, wherein the R1 or R2 group comprises at
least one of:
--CH.sub.2OCH.sub.3;--CF.sub.2OCH.sub.3;--CF.sub.2OCF.sub.3;--CH.-
sub.2CH.sub.2OCH.sub.3;--CH.sub.2CF.sub.2OCH.sub.3;--CF.sub.2CH.sub.2OCH.s-
ub.3;
--CF.sub.2CF.sub.2OCH.sub.3;--CF.sub.2CF.sub.2OCF.sub.3;--CF.sub.2CH-
.sub.2OCF.sub.3;--CH.sub.2CF.sub.2OCF.sub.3;--CH.sub.2CH.sub.2OCF.sub.3;
--CHFCF.sub.2OCF.sub.2H;--CF.sub.2CF.sub.2OCF(CF.sub.3).sub.2;--CF.sub.2C-
H.sub.2OCF(CF.sub.3).sub.2;--CH.sub.2CF.sub.2OCF(CF.sub.3).sub.2;
--CH.sub.2CH.sub.2OCF(CF.sub.3).sub.2;--CF.sub.2CF.sub.2OC(CF.sub.3).sub.-
3;
--CF.sub.2CH.sub.2OC(CF.sub.3).sub.3;--CH.sub.2CF.sub.2OC(CF.sub.3).sub-
.3;
--CH.sub.2CH.sub.2OC(CF.sub.3).sub.3;--CH.sub.2CH.sub.2OCH.sub.2CH.sub-
.3;--CH.sub.2CH.sub.2OCH.sub.2CF.sub.3;--CH.sub.2CH.sub.2OCF.sub.2CH.sub.3-
;
--CH.sub.2CH.sub.2OCF.sub.2CF.sub.3;--CH.sub.2CF.sub.2OCH.sub.2CH.sub.3;-
--CH.sub.2CF.sub.2OCF.sub.2CH.sub.3;--CH.sub.2CF.sub.2OCH.sub.2CF.sub.3;
--CH.sub.2CF.sub.2OCF.sub.2CF.sub.3;--CF.sub.2CH.sub.2OCH.sub.2CH.sub.3;--
-CF.sub.2CH.sub.2OCF.sub.2CH.sub.3;--CF.sub.2CH.sub.2OCH.sub.2CF.sub.3;
--CF.sub.2CH.sub.2OCF.sub.2CF.sub.3;--CF.sub.2CF.sub.2OCH.sub.2CH.sub.3;--
-CF.sub.2CF.sub.2OCF.sub.2CH.sub.3;--CF.sub.2CF.sub.2OCH.sub.2CF.sub.3;
--CF.sub.2CF.sub.2OCF.sub.2CF.sub.3;--CF.sub.2CF.sub.2CF.sub.2OCH.sub.3;--
-CF.sub.2CF.sub.2CH.sub.2OCH.sub.3;--CF.sub.2CH.sub.2CF.sub.2OCH.sub.3;
--CH.sub.2CF.sub.2CF.sub.2OCH.sub.3;--CH.sub.2CF.sub.2CH.sub.2OCH.sub.3;--
-CH.sub.2CH.sub.2CF.sub.2OCH.sub.3;--CF.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;--CF.sub.2CF.sub.2CF.sub.2OCF.sub.3;--
-CF.sub.2CF.sub.2CH.sub.2OCF.sub.3;--CF.sub.2CH.sub.2CF.sub.2OCF.sub.3;
--CH.sub.2CF.sub.2CF.sub.2OCF.sub.3;--CH.sub.2CH.sub.2CF.sub.2OCF.sub.3;--
-CH.sub.2CF.sub.2CH.sub.2OCF.sub.3;--CF.sub.2CH.sub.2CH.sub.2OCF.sub.3;
--CH.sub.2CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;--CH.sub.2CH.sub.2CH.sub.2CH.-
sub.2CH.sub.2OCH.sub.3;--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2O-
CH.sub.3;
--CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.3;--CH.sub.2CH.sub.2O-
CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.3.
32. The method of claim 29, wherein the R1 group comprises at least
one of: methyl (--CH.sub.3); ethyl (--CH.sub.2CH.sub.3); n-propyl
(--CH.sub.2CH.sub.2CH.sub.3); n-butyl
(--CH.sub.2CH.sub.2CH.sub.2CH.sub.3); n-pentyl
(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3); n-hexyl
(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3); n-heptyl
(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3);
iso-propyl (--CH(CH.sub.3).sub.2); iso-butyl
(--CH.sub.2CH(CH.sub.3).sub.2); sec-butyl
(--CH(CH.sub.3)CH.sub.2CH.sub.3); tert-butyl (--C(CH.sub.3).sub.3);
iso-pentyl (--CH.sub.2CH.sub.2CH(CH.sub.3).sub.2); trifluoromethyl
(--CF.sub.3);2,2,2-trifluoroethyl
(--CH.sub.2CF.sub.3);1,1-difluoroethyl (--CF.sub.2CH.sub.3);
perfluoroethyl (--CF.sub.2CF.sub.3); 3,3,3-trifluoro-n-propyl
(--CH.sub.2CH.sub.2CF.sub.3);2,2-difluoro-n-propyl (-CH.sub.2
CF.sub.2 CH.sub.3);1,1-difluoro-n-propyl (--CF.sub.2 CH.sub.2
CH.sub.3);1,1,3,3,3-pentafluoro-n-propyl (--CF.sub.2 CH.sub.2
CF.sub.3);2,2,3,3,3-pentafluoro-n-propyl
(--CH.sub.2CF.sub.2CF.sub.3); perfluoro-n-propyl
(--CF.sub.2CF.sub.2CF.sub.3); perfluoro-n-butyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.3); perfluoro-n-pentyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3); perfluoro-n-hexyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3);
perfluoro-n-heptyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3);--CF(CH.sub.-
3).sub.2;--CH(CH.sub.3)CF.sub.3;--CF(CF.sub.3).sub.2;
--CH(CF.sub.3).sub.2;--CH.sub.2CF(CH.sub.3).sub.2;--CF.sub.2CH(CH.sub.3).-
sub.2;--CH.sub.2CH(CH.sub.3)CF.sub.3;--CH.sub.2CH(CF.sub.3).sub.2;--CF.sub-
.2CF(CF.sub.3).sub.2; --C(CF.sub.3).sub.3.
Description
TECHNICAL FIELD
The present specification relates to electric current-producing
devices and techniques including non-aqueous electrolyte solvents
for use in electric current-producing devices.
BACKGROUND
Batteries are commonly used to power many types of motors and
electronic devices for use in portable applications. The battery
may be rechargeable or disposable (one-shot usage) type. The
battery provides operating power for integrated circuits in
portable electronic systems, or provides an electromotive force to
drive motors for industrial applications.
One area of particular interest is automotive power trains.
Battery-powered automobiles offer many interesting possibilities
for fulfilling transportation needs, while reducing energy
consumption, and minimizing hazard to the environment. Automobile
batteries must be rechargeable and preferably deliver high
voltages, e.g. greater than 4.5 VDC, to provide adequate power to
the motor. The battery should also have good electrochemical
stability, safety and longevity.
Common types of rechargeable battery are known as lithium-ion cell
and lithium metal cell. U.S. Pat. Nos. 5,460,905; 5,462,566;
5,582,623; and 5,587,253 describe the basic elements and
performance requirements of lithium batteries and their components.
A key issue in the development of high energy batteries is the
choice of the electrolyte element to improve the possible output
voltage, stability, cycle life, and safety of the battery. A large
number of non-aqueous organic solvents have been suggested and
investigated as electrolytes in connection with various types of
cells containing lithium electrodes. U.S. Pat. Nos. 3,185,590;
3,578,500; 3,778,310; 3,877,983; 4,163,829; 4,118,550; 4,252,876;
4,499,161; 4,740,436; and 5,079,109 describe many possible
electrolyte element combinations and electrolyte solvents, such as
borates, substituted and unsubstituted ethers, cyclic ethers,
polyethers, esters, sulfones, alkylene carbonates, organic
sulfites, organic sulfates, organic nitrites and organic nitro
compounds.
One class of organic electrolyte solvents that have received
attention as a component of electrolyte elements for
electrochemical cells and other devices are the sulfones. Sulfones
can generally be divided into two types: the aromatic sulfones and
the aliphatic sulfones. The aliphatic sulfones can also be divided
into two types-the cyclic (commonly referred to as sulfolanes) and
non-cyclic. The non-cyclic aliphatic sulfones form a
potentially-attractive group of organic solvents that present a
high chemical and thermal stability.
In particular, ethyl methyl sulfone (EMS) has shown remarkable
electrochemical stability, reaching 5.8v vs. Li/Li.sup.+ by a
conservative stability criterion. For example, 2M LiPF.sub.6/EMS
has been used as the supporting electrolyte in a dual graphite cell
which operates around 5.5v, and 1M LiPF.sub.6/EMS has been used as
the electrolyte in Li/T2-Li.sub.2/3[Ni.sub.1/3Mn.sub.2/3]O.sub.2
cell which operates up to 5.4v. Despite its success as solvent in
those cases, EMS applications are limited by a shortcoming, i.e.
its relatively high melting point, 36.5.degree. C., which
eliminates its use as a single solvent in electronic devices whose
range of operation includes temperatures much below ambient. To
overcome this limitation EMS must be blended with other high
stability solvents that yield low-melting eutectics with EMS, or be
replaced by alternative sulfones with lower melting points.
A eutectic mixture of EMS with dimethyl sulfone melts at 25.degree.
C., and the mixture has been used in lithium salt solution
conductivity studies extending well below ambient, however,
crystallization takes place on long exposure to low temperatures.
Since single solvent electrolytes are desirable for a variety of
reasons, and since alternative second components to provide
lower-melting eutectics than the above are also desirable, a need
exists to further study the synthesis of sulfone-containing
molecular liquids.
SUMMARY
In one embodiment, the present specification discloses an
electrolyte element for use in an electric current-producing device
comprising one or more ionic electrolyte salts and a non-aqueous
electrolyte solvent including one or more non-symmetrical,
non-cyclic sulfones of the general formula: R1--SO2--R2. The R1
group is a linear or branched alkyl or partially or fully
fluorinated linear or branched alkyl group having 1 to 7 carbon
atoms. The R2 group, which is different in formulation than the R1
group, is a linear or branched or partially or fully fluorinated
linear or branched oxygen containing alkyl group having 1 to 7
carbon atoms.
In another embodiment, the present specification discloses an
electric current-producing device comprising a cathode and an
anode. A non-aqueous electrolyte element is disposed between the
cathode and anode. The non-aqueous electrolyte element includes an
electrolyte salt and a non-symmetrical, non-cyclic sulfone of the
general formula: R1--SO2--R2. R1 is an alkyl group, and R2 is an
alkyl group including oxygen.
In another embodiment, the present specification discloses an
electrolyte for a electric current-producing device comprising an
non-aqueous electrolyte solvent including an non-symmetrical,
non-cyclic sulfone of the general formula: R1--SO2--R2. R1 is an
alkyl group, and R2 is an alkyl group including oxygen.
In another embodiment, the present specification discloses a method
of forming an electric current-producing device, comprising the
steps of providing a cathode, providing an anode, and providing a
non-aqueous electrolyte element disposed between the cathode and
anode. The non-aqueous electrolyte element includes an electrolyte
salt and a non-symmetrical, non-cyclic sulfone of the general
formula: R1--SO2--R2. R1 is an alkyl group, and R2 is an alkyl
group including oxygen.
In yet another embodiment, the present specification discloses an
electrolytic solvent comprising a sulfone compound and being
configured to exhibit high chemical and thermal stability and high
oxidation resistance. Such a sulfone may have be represented by a
chemical formula of: R1--SO.sub.2--R2 wherein R.sup.1 is an alkyl
group and R.sup.2 is a partially oxygenated alkyl group. This
electrolytic solvent may be combined with ionic salts, co-solvents,
or other additives and may be used as an electrolyte element in an
electric current producing device. This sulfone-based electrolyte
can be used in an electric current producing device to generate
high output voltages and maintain high oxidation resistance.
Therefore, such a sulfone-based electrolyte can be implemented in
electrolytic cells, rechargeable batteries, electric capacitors,
fuel cells, and the like which comprise non-aqueous electrolyte
elements to provide high energy storage capacity, long cycle life,
and a low rate of self-discharge, with good thermal stability.
In yet another implementation, the present specification provides
an electrolyte solvent of the formula: R.sup.1--SO.sub.2--R.sup.2,
wherein R.sup.1 and R.sup.2 are alkyl groups that are at least
partially oxygenated. Such a solvent can be used in an electric
current-producing devices and other devices.
In yet another implementation, the present specification provides
an electrolyte solvent of the formula: R.sup.1--SO.sub.2--R ,
wherein R.sup.1 is an alkyl group, R.sup.2 is an alkyl group that
is at least partially oxygenated, and R.sup.1, R.sup.2, or both are
partially or fully fluorinated. Such a solvent can be used in an
electric current-producing devices and other devices
In yet another implementation, the present specification provides
an electrolyte comprising one or more ionic electrolyte salts and a
solvent of the formula: R.sup.1--SO.sub.2--R.sup.2, wherein R.sup.1
is an alkyl group and R.sup.2 is an alkyl group that is at least
partially oxygenated. Such an electrolyte can be used in an
electric current-producing devices and other devices
Various features described in the present specification can be used
to provide an electrolyte solution which combines high oxidation
resistance and high ambient temperature conductivity, an
electrolyte solution which exhibits exceptionally high conductivity
and high chemical and electrochemical stability. An electrolyte
solvent described in the present specification may also be combined
with one or more ionic salts, one or more liquid co-solvents,
gelling agents, ionically conductive solid polymers, and other
additives.
These and other embodiments and implementations are described in
detail in the drawing, the description and the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a lithium battery providing power to a load;
FIG. 2 illustrates non-symmetrical, non-cyclic sulfone group
coupled with a R1 alkyl group and R2 oxygen containing alkyl
group;
FIG. 3 is a graph of conductivities of 1M LiTFSI in different
sulfones;
FIGS. 4a-4b are graphs of electrochemical stability ranges
("windows") for 1M LiTFSI in different sulfone solutions;
FIG. 5 is a graph of performance of the cell MCMB25-28|1M
LiPF.sub.6/EMES|Li under the current density of 0.013 mA
cm.sup.-2;
FIGS. 6a-6b are graphs of cell performance under different current
densities;
FIG. 7 is a graph of charge/discharge capacity and coulomb
efficiency of the cell LiCro.sub.0.015Mn.sub.1.985O.sub.4|1M
LiPF.sub.6/EMES|Li under the current density of 0.092 mA
cm.sup.-2;
FIGS. 8a-8b are graphs of charge and discharge profile of half cell
of Li||Graphite and full cell of Graphite||LiCoO.sub.2 using 1.0M
LiPF.sub.6/EMES as the electrolyte, respectively;
FIGS. 9a-9b are graphs of temperature dependence of ionic
conductivities of 1.0M lithium salts, A) 1.0M lithium salts in EMES
containing 5 wt % carbonates (EC and DMC) and ethylene sulfite(ES);
B) 1.0MLiPF.sub.6 in EMES containing different percentage of
EC;
FIGS. 10a-10d are graphs of cyclic voltammograms for 1M LiPF.sub.6
in different EMES/EC mixtures, A) 5 wt % EC; B) 10 wt % EC; C) 20
wt % EC; D) 30 wt % EC;
FIGS. 11a-11d are graphs of cyclic voltammograms for 1M LiPF.sub.6
in different EMES/DMC mixtures, A) 5 wt % DMC; B) 10 wt % DMC; C)
20 wt % DMC; D) 30 wt % DMC;
FIG. 12 is a graph of a first lithium intercalation and
de-intercalation profile on graphite electrode using different 1.0M
LiPF.sub.6 electrolyte solutions;
FIG. 13 is a graph of a first charge and discharge profile of full
cell of graphite ||LiCoO.sub.2 using different 1.0M LiPF.sub.6
electrolyte solutions; and
FIG. 14 is a graph of an electrochemical window for 1M LiClO.sub.4
in EMES/ES mixture.
DETAILED DESCRIPTION OF THE DRAWINGS
The present invention is described in one or more embodiments in
the following description with reference to the Figures, in which
like numerals represent the same or similar elements. While the
invention is described in terms of the best mode for achieving the
invention's objectives, it will be appreciated by those skilled in
the art that it is intended to cover alternatives, modifications,
and equivalents as may be included within the spirit and scope of
the invention as defined by the appended claims and their
equivalents as supported by the following disclosure and
drawings.
Batteries are commonly used to power many types of electronics,
motors, and other devices for use in portable applications. The
battery may be rechargeable or disposable one-shot usage type. The
battery provides operating power for integrated circuits in
portable electronic systems, or an electromotive force to drive
motors for industrial and automotive applications.
FIG. 1 illustrates electric current-producing device 10 providing
electrical power to load 12. In one embodiment, the electric
current-producing device 10 is a battery or other voltaic cell.
Alternatively, the electric current-producing device 10 is a
supercapacitor. Device 10 may include a lithium-ion cell or lithium
metal cell, or plurality of such cells. Device 10 has anode 14,
cathode 16, and electrolyte 18. Anode 14 and cathode 16 are
connected to load 12 to provide electrical power to the load.
Electrolyte 18 contains a non-aqueous electrolyte element
comprising a non-symmetrical, non-cyclic sulfone component, as
described fully hereinafter, that is stable in the presence of the
anode and cathode. Load 12 may be an electronic system, equipment
in an industrial application, or motor for an automobile, just to
name a few.
The material of anode 14 has one or more metals or metal alloys
selected from the Group IA and IIA metals in the Periodic Table.
For example, anode 14 may be made with lithium or sodium. The anode
may also be alkali-metal intercalated carbon, such as LiCx where x
is equal to or greater than 2. Also useful as anode materials are
alkali-metal intercalated conductive polymers, such as lithium,
sodium or potassium doped polyacetylenes, polyphenylenes,
polyquinolines, and the like. Examples of other suitable anode
material are lithium metal, lithium-aluminum alloys, lithium-tin
alloys, lithium-intercalated carbons, lithium-intercalated
graphites, calcium metal, aluminum, sodium, and sodium alloys.
Cathode 16 may be made with any of the commonly used cathode active
materials. Examples of suitable cathode active materials are
inorganic insertion oxides and sulfides, metal chalcogenides,
elemental sulfur, organo-sulfur and carbon-sulfur polymers,
conjugated polymers, and liquid cathodes. Useful inorganic
insertion oxides include CoO2, NiO2, MnO2, Mn204, V6O13, V2O5, and
blends thereof. Useful inorganic sulfides include TiS2, MoS2, and
the like. Suitable conjugated polymers include polyacetylene,
poly(phenylene vinylene), and polyaniline. Useful liquid cathodes
include SO2, SOC12, SO2C12, and POC13. Useful organo-sulfur
materials include those disclosed in U.S. Pat. Nos. 4,833,048;
4,917,974; 5,324,599; and 5,516,598.
Further examples of useful cathode active materials include
organo-sulfur polymer materials, as described in U.S. Pat. No.
5,441,831, and carbon-sulfur materials, as described in U.S. Pat.
Nos. 5,601,947 and 5,529,860. Sulfur containing cathode active
organic materials as described in these disclosures comprise, in
their oxidized state, a polysulfide moiety of the formula, -5m-,
wherein m is an integer equal to or greater than 3. Further useful
composite cathode compositions including organo-sulfur or elemental
sulfur. Cathode 16 may further comprise one or more materials which
include: binders, electrolytes, and conductive additives, usually
to improve or simplify their fabrication as well as improve their
electrical and electrochemical characteristics.
Useful conductive additives are those known to one skilled in the
art of electrode fabrication and are such that they provide
electrical connectivity to the majority of the electroactive
materials in the composite cathode. Examples of useful conductive
fillers include conductive carbons (e.g., carbon black), graphites,
metal flakes, metal powders, electrically conductive polymers, and
the like.
In those cases where binder and conductive filler are desired, the
amounts of binder and conductive filler can vary widely and the
amounts present will depend on the desired performance. Typically,
when binders and conductive fillers are used, the amount of binder
will vary greatly, but will generally be less than about 15 wt % of
the composite cathode. The amount of conductive filler used will
also vary greatly and will typically be less than 20 wt % of the
composite cathode. Useful amounts of conductive additives are
generally less than 12 wt %.
The choice of binder material may vary widely so long as it is
inert with respect to the composite cathode materials. Useful
binders are those materials, usually polymeric, that allow for ease
of processing of battery electrode composites. Examples of useful
binders are organic polymers such as
polytetrafluoroethylenes(TEFLONTM), polyvinylidine fluorides (PVF2
or PVDF), ethylene-propylene-diene (EPDM) rubbers, polyethylene
oxides (PEO), UV curable acrylates, UV curable methacrylates, and
UV curable divinylethers, and the like.
For the case of the automotive application, battery-powered motors
offer many interesting possibilities for fulfilling transportation
needs with greater efficiency and reduced harm to the environment.
Automobile batteries must be rechargeable and preferably deliver
high voltages, e.g. greater than 4.5 VDC, to provide adequate power
to the motor. The battery should also have good electrochemical
stability and longevity. Electrolyte 18 plays an important role in
the electrochemical performance of electric current-producing
device 10, including the ability to generate high output voltages
for maximum power transfer.
Electrolyte elements are useful in electrolytic cells, rechargeable
batteries, electric capacitors, fuel cells, and function as a
medium for storage and transport of ions. The term "electrolyte
element," as used herein, relates to an element of an electric
current-producing device which comprises an electrolyte solvent,
one or more electrolyte salts, and optionally other additives
including polymer electrolytes and gel-polymer electrolytes. Any
liquid, solid, or solid-like material capable of storing and
transporting ions may be used, so long as the material is
chemically inert with respect to anode 14 and cathode 16, and the
material facilitates the transportation of ions between the anode
and the cathode. In the special case of solid electrolytes, these
materials may additionally function as separator materials between
the anode and cathode.
The electrolyte elements of the present invention include one or
more ionic electrolyte salts and a non-aqueous electrolyte solvent.
The non-aqueous electrolyte solvent contains one or more
non-symmetrical, non-cyclic sulfones, and optionally other
additives, such as one or more electrolyte co-solvents, gelling
agents, ionically conductive solid polymers, and/or other
additives. The electrolyte elements may be prepared by dissolving
one or more ionic electrolyte salts in one or more non-aqueous
electrolyte solvents.
As a feature of the present invention, a new sulfone is introduced
into the composition of electrolyte 18. The sulfones are provided
in the battery electrolyte to increase the possible output voltage
and available power from the battery. In particular, sulfones with
different length of oligo ethylene glycol segments have been
synthesized and tested for use in rechargeable lithium batteries.
Relative to the model compound EMS, which has a melting point of
36.5.degree. C., the new sulfones have low melting points, mostly
depressed below room temperature. Their conductivities are lower
than that of EMS. The highest ambient temperature conductivity of
10.sup.-2.58S.cm.sup.-1 is obtained for 0.7M LiTFSI/MEMS solution.
The sulfones show wide electrochemical stability windows, in excess
of 5.0v vs Li/Li.sup.+, increasing with decreasing length of the
oligoether chains. A cell with lithium metal anode and manganate
cathode performed well, maintaining high coulomb efficiency over
200 cycles.
The non-aqueous electrolyte solvents include a non-symmetrical,
non-cyclic sulfone, suitable for use in electric current-producing
devices, such as device 10. As shown in FIG. 2, the
non-symmetrical, non-cyclic sulfone has the general formula:
R1--SO2--R2. The SO2 group 20 represents the sulfone group. The R1
group 22 is a linear or branched alkyl or partially or fully
fluorinated linear or branched alkyl group having 1 to 7 carbon
atoms. The R2 group 24 is a linear or branched or partially or
fully fluorinated linear or branched alkyl group containing oxygen
and having 1 to 7 carbon atoms. In another embodiment, the R1 and
R2 groups each have 1 to 4 carbon atoms.
The SO2 sulfone group is the same group that occurs in the
following compounds: ethylmethyl sulfone (EMSF, CH3CH2--SO2--CH3),
ethyl-iso-propyl sulfone (EiPSF, CH3CH2--SO2--CH(CH3)2),
ethyl-sec-butyl sulfone (EsB SF, CH3CH2--SO2--CH(CH3)(CH2CH3)),
ethyl-iso-butyl sulfone (EiBSF).
Examples of the R1 alkyl group are: methyl (--CH.sub.3); ethyl
(--CH.sub.2CH.sub.3); n-propyl (--CH.sub.2CH.sub.2CH.sub.3);
n-butyl (--CH.sub.2CH.sub.2CH.sub.2CH.sub.3); n-pentyl
(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3); n-hexyl
(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3); n-heptyl
(--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.3);
iso-propyl (--CH(CH.sub.3) .sub.2); iso-butyl
(--CH.sub.2CH(CH.sub.3).sub.2); sec-butyl
(--CH(CH.sub.3)CH.sub.2CH.sub.3); tert-butyl (--C(CH.sub.3).sub.3);
iso-pentyl (--CH.sub.2CH.sub.2CH(CH.sub.3).sub.2); trifluoromethyl
(--CF.sub.3); 2,2,2-trifluoroethyl (--CH.sub.2CF.sub.3); 1,
1-difluoroethyl (--CF.sub.2CH.sub.3); perfluoroethyl
(--CF.sub.2CF.sub.3); 3,3,3-trifluoro-n-propyl
(--CH.sub.2CH.sub.2CF.sub.3); 2,2-difluoro-n-propyl
(--CH.sub.2CF.sub.2CH.sub.3); 1,1-difluoro-n-propyl
(--CF.sub.2CH.sub.2CH.sub.3); 1,1,3,3,3-pentafluoro-n-propyl
(--CF.sub.2CH.sub.2CF.sub.3); 2,2,3,3,3- pentafluoro-n-propyl
(--CH.sub.2CF.sub.2CF.sub.3); perfluoro-n-propyl
(--CF.sub.2CF.sub.2CF.sub.3); perfluoro-n-butyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.3); perfluoro-n-pentyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3); perfluoro-n-hexyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3);
perfluoro-n-heptyl
(--CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3);
--CF(CH.sub.3)2;--CH(CH.sub.3)CF.sub.3; --CF(CF.sub.3).sub.2;
--CH(CF.sub.3)2;--CH.sub.2CF(CH.sub.3)2;--CF.sub.2CH(CH.sub.3)2;--CH.sub.-
2CH(CH.sub.3)CF.sub.3; --CH.sub.2CH(CF.sub.3).sub.2;
--CF.sub.2CF(CF.sub.3).sub.2; --C(CF.sub.3).sub.3.
Examples of the R2 oxygen containing alkyl group are:
--CH.sub.2OCH.sub.3; --CF.sub.2OCH.sub.3; --CF.sub.2OCF.sub.3;
--CH.sub.2CH.sub.2OCH.sub.3; --CH.sub.2CF.sub.2OCH.sub.3;
--CF.sub.2CH.sub.2OCH.sub.3; --CF.sub.2CF.sub.2OCH.sub.3;
--CF.sub.2CF.sub.2OCF.sub.3; --CF.sub.2CH.sub.2OCF.sub.3;
--CH.sub.2CF.sub.2OCF.sub.3; --CH.sub.2CH.sub.2OCF.sub.3;
--CHFCF.sub.2OCF.sub.2H; --CF.sub.2CF.sub.2OCF(CF.sub.3).sub.2;
--CF.sub.2CH.sub.2OCF(CF.sub.3).sub.2;
--CH.sub.2CF.sub.2OCF(CF.sub.3).sub.2;
--CH.sub.2CH.sub.2OCF(CF.sub.3).sub.2;
--CF.sub.2CF.sub.2OC(CF.sub.3).sub.3;
--CF.sub.2CH.sub.2OC(CF.sub.3).sub.3;
--CH.sub.2CF.sub.2OC(CF.sub.3).sub.3;
--CH.sub.2CH.sub.2OC(CF.sub.3).sub.3;
--CH.sub.2CH.sub.2OCH.sub.2CH.sub.3;
--CH.sub.2CH.sub.2OCH.sub.2CF.sub.3;
--CH.sub.2CH.sub.2OCF.sub.2CH.sub.3;
--CH.sub.2CH.sub.2OCF.sub.2CF.sub.3;
--CH.sub.2CF.sub.2OCH.sub.2CH.sub.3;
--CH.sub.2CF.sub.2OCF.sub.2CH.sub.3;
--CH.sub.2CF.sub.2OCH.sub.2CF.sub.3;
--CH.sub.2CF.sub.2OCF.sub.2CF.sub.3;
--CF.sub.2CH.sub.2OCH.sub.2CH.sub.3;
--CF.sub.2CH.sub.2OCF.sub.2CH.sub.3;
--CF.sub.2CH.sub.2OCH.sub.2CF.sub.3;
--CF.sub.2CH.sub.2OCF.sub.2CF.sub.3;
--CF.sub.2CF.sub.2OCH.sub.2CH.sub.3;
--CF.sub.2CF.sub.2OCF.sub.2CH.sub.3;
--CF.sub.2CF.sub.2OCH.sub.2CF.sub.3;
--CF.sub.2CF.sub.2OCF.sub.2CF.sub.3;
--CF.sub.2CF.sub.2CF.sub.2OCH.sub.3;
--CF.sub.2CF.sub.2CH.sub.2OCH.sub.3;
--CF.sub.2CH.sub.2CF.sub.2OCH.sub.3;
--CH.sub.2CF.sub.2CF.sub.2OCH.sub.3;
--CH.sub.2CF.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2CF.sub.2OCH.sub.3;
--CF.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CF.sub.2CF.sub.2CF.sub.2OCF.sub.3;
--CF.sub.2CF.sub.2CH.sub.2OCF.sub.3;
--CF.sub.2CH.sub.2CF.sub.2OCF.sub.3;
--CH.sub.2CF.sub.2CF.sub.2OCF.sub.3;
--CH.sub.2CH.sub.2CF.sub.2OCF.sub.3;
--CH.sub.2CF.sub.2CH.sub.2OCF.sub.3;
--CF.sub.2CH.sub.2CH.sub.2OCF.sub.3;
--CH.sub.2CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.3;
--CH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.3.
In an alternate embodiment, the R1 alkyl group may also contain
oxygen, e.g. using any one of the formulations described for the R2
group. However, the R1 and R2 groups will each have a different
formulation from the other, e.g. in terms of chemical structure or
length of segments.
One group of electrolyte salts includes MClO.sub.4, MPF.sub.6,
MPF.sub.x(C.sub.nF.sub.2n+1).sub.6-x, MBF.sub.4,
MBF.sub.4-x(C.sub.nF.sub.2n+1).sub.x, MAsF.sub.6, MSCN,
MB(CO.sub.2).sub.4 ("LiBOB"), and MSO.sub.3CF.sub.3, where "M"
represents lithium or sodium. Also available are electrolyte
solutions including MN(SO.sub.2CF.sub.3).sub.2 as the electrolyte
salt, which exhibits exceptionally high conductivity combined with
high chemical and electrochemical stability.
The electrolyte elements may further include one or more liquid
electrolye co-solvents (i.e., in addition to a non-symmetrical,
non-cyclic sulfone), gelling agents, ionically conductive solid
polymers, and other additives. Suitable electrolyte co-solvents,
gelling agents or ionically conductive solid polymers include any
of those commonly used with lithium metal and lithium-ion cells.
For example, suitable liquid electrolyte co-solvents for use in the
electrolyte elements include any one of the commonly used
electrolyte solvents. Examples of useful liquid electrolyte
co-solvents include carbonates, N-methyl acetamide, acetonitrile,
symmetric sulfones, sulfolanes, 1,3-dioxolanes, glymes,
polyethylene glycols, siloxanes, and ethylene oxide grafted
siloxanes, and blends thereof. Examples of useful carbonates
include ethylene carbonate (EC) and propylene carbonate (PC).
Examples of useful glymes includes tetraethyleneglycol dimethyl
ether (TEGDME) and 1,2-dimethoxyethane.
Liquid electrolyte elements are often used in combination with one
of the common porous separators. Liquid electrolyte solvents or
plasticizing agents are often themselves useful as gel forming
agents for gel-polymer electrolytes. Examples of gelling agents
which are useful in the electrolyte elements are those prepared
from polymer matrices derived from polyethylene oxides (PEO),
polypropylene oxides, polyacrylonitriles, polysiloxanes,
polyimides, polyethers, sulfonated polyimides, perfluorinated
membranes (NafionTM resins), polyeFthylene glycols, polyethylene
glycol-bis-(methyl acrylates), polyethylene glycol-bis(methyl
methacrylates), derivatives of the foregoing, copolymers of the
foregoing, crosslinked and network structures of the foregoing,
blends of the foregoing, and the like.
Examples of ionically conductive solid polymers suitable for use in
the electrolyte elements are those having polyethers, polyethylene
oxides (PEO), polyimides, polyphosphazenes, polyacrylonitriles
(PAN), polysiloxanes, polyether grafted polysiloxanes, derivatives
of the foregoing, copolymers of the foregoing, crosslinked and
network structures of the foregoing, and blends of the foregoing,
to which is added an appropriate ionic electrolyte salt. Ionically
conductive solid polymers electrolytes may additionally function as
separator materials between the anode and cathode.
Other additives which are useful in the electrolyte elements
include soluble additives, such as: vinylene carbonate (VC),
ethylene sulfite (ES), propylene sulfite (PS), fluoroethylen
sulfite (FEC), .alpha.-bromo-.gamma.-butyrolactone, methyl
chloroformate, t-butylene carbonate, 12-crown-4, carbon dioxide
(CO.sub.2), sulfur dioxide (SO.sub.2), sulfur trioxide and other
inorganic additives; acid anhydrides to reduce or eliminate the
presence of water; reaction products of carbon disulfide and
lithium, possibly a soluble sulfide, as disclosed in U.S. Pat. No.
3,532,543; high concentrations of water as described in U.S. Pat.
Nos. 5,432,425 and 5,436,549; and polysulfide additives.
The non-aqueous electrolyte solvents are particularly useful in
electrolytic cells, rechargeable batteries, electric capacitors,
fuel cells, and the like, which comprise non-aqueous electrolyte
elements and which require high energy storage capacity, long shelf
life, and a low rate of self-discharge. The electrolyte solvents
are particularly useful in electrolytic cells comprising
alkali-metal-containing electrodes, and particularly to lithium
intercalation electrodes.
The high oxidation resistance of the ambient temperature
electrolyte solutions of the present invention result from the
stability of the --SO2-- group when in a non-cyclic, non-symmetric
sulfone structure, characterized by freezing temperatures low
enough to enable utilization in ambient temperature applications.
When such a sulfone is utilized as a solvent to dissolve inorganic
electrolyte salts of highly oxidation resistant anions such as
ClO4, CF3SO3 (triflate), and in particular, bis(trifluoromethane
sulfonyl) imide(--N(CF3SO2)2, lithium imide), then solutions which
combine exceptional oxidation resistance with high ambient
temperature conductivity are obtained as, for example, shown in
FIG. 3. In general, FIG. 3 illustrates the DC electrical
conductivities of electrolytes of various solutions of alkali metal
salts in sulfones. As seen in the figure, at 25.degree. C. the
conductivity of EMS is more than half order of magnitude higher
than those of the oligoether sulfones of the present work,
indicating the great advantage of EMS as a single solvent in the
sulfone family.
The process of making, using, and testing electric
current-producing device 10, including anode 14, cathode 16, and
electrolyte 18 containing the non-aqueous electrolyte solvents
having non-symmetrical, non-cyclic sulfone groups defined above by
R1-SO2-R2 is now described in detail.
Oligoether-containing sulfides were synthesized by reacting halide
compounds of oligoethylene glycols with sodium methanethiolate or
with sodium ethanethiolate. Sulfones with structures listed in
Table 1 were obtained by oxidation of the synthesized sulfides with
H.sub.2O.sub.2. Table 1 is summary of physical properties of
synthesized sulfones, wherein note.sup.1 is estimated melting
point, note.sup.2 is boiling point under atmosphere pressure
estimated by nomograph, and note.sup.3 is estimated boiling
point.
TABLE-US-00001 TABLE 1 m.p b.p Sulfones (.degree. C.) (.degree. C.)
T.sub.g(.degree. C.) CH.sub.3CH.sub.2SO.sub.2CH.sub.3 (EMS) 36.5
85~87/4.0 -- mm (~240).sup.2
CH.sub.3OCH.sub.2CH.sub.2SO.sub.2CH.sub.3 (MEMS) 15.0 96~98/1.0
-89.5 mm (~275).sup.2
CH.sub.3OCH.sub.2CH.sub.2SO.sub.2C.sub.2H.sub.5 (EMES) 2.0
103~105/1.0 -91.0 mm (~286).sup.2
CH.sub.3(OCH.sub.2CH.sub.2).sub.2SO.sub.2C.sub.2H.sub.5 <0.sup.1
>29- 0.sup.3 -87.6 (EMEES)
CH.sub.3(OCH.sub.2CH.sub.2).sub.3SO.sub.2C.sub.2H.sub.5 <0.sup.1
>29- 0.sup.3 -82.5 (EMEEES)
CH.sub.3OCH.sub.2CH.sub.2SO.sub.2CH.sub.2CH.sub.2OCH.sub.3 47.0
>290.su- p.3 -90.7 (DMES)
Glass transition temperature T.sub.g was measured using a DTA
instrument. The heating rate was 10K/min. T.sub.g was defined as
the onset temperature of the heat capacity jump and T.sub.m was
defined as the temperature at which the melting peak reaches its
maximum. The boiling point was recorded during the distillation
process.
Electrolyte solutions of different salt concentrations were
prepared by dissolving calculated amount of lithium salts in the
respective sulfones. The measurement of DC conductivity was carried
out using an automated frequency impedance analyzer. The
measurements were made automatically during heating of the
precooled samples at 1K/min by means of a programmed controller. To
determine electrochemical characteristics, cyclic voltammetry was
performed using a potentiostat/galvanostat with a three-electrode
cell. The working electrode was a platinum wire, and the counter
and reference electrodes were lithium foil in the voltage range of
-0.3-6.0V. Most scans were made at room temperature at a typical
scan rate of 1 mv/s.
Electrochemical half cells, Li|| sulfone electrolyte|| MCMB25-28
(MCMB for mesocarbon microbeads), and Li|| sulfone electrolyte||
LiCro.sub.0.015Mn.sub.1.985O.sub.4 were constructed using
fiberglass paper as the separator. The cathode solution having 82%
active material, 10% carbon black and 8% PVdF in
N-methylpyrrolindone was cast directly on the pre-weighed stainless
steel electrode. The electrode was dried, first at room temperature
and then at 100.degree. C. under vacuum for two days. The weight of
the electrode was determined inside the dry box, and the weight of
active material obtained by difference. The anode composite
electrodes were made in a similar way from a slurry of 90%
MCMB25-28 and 10% PVdF in N-methylpyrrolindone. The cell
construction and the tests were all carried out in an argon-filled
glove box. The voltage profile of the charge/discharge process was
monitored using a battery cycler. A constant current ranging from
0.01.about.0.1 mA/cm.sup.2 was used with pre-set cut-off voltage of
0.01.about.2.0V for Li || electrolyte || MCMB25-28 cell and
3.0.about.4.3V for Li || electrolyte ||
LiCr.sub.0.015Mn.sub.1.985O.sub.4 cell. At these cut-off voltages a
computerized cycler automatically switched the test cells to charge
or discharge.
All of the ether fragment additions caused the lowering of melting
point relative to EMS except for one case (dimethoxyethyl sulfone)
in which symmetry was retained. Indeed, in some cases
crystallization was not observed at all. For instance, introduction
of the smallest fragment, the methoxy group, at the ethyl end of
EMS yielding methoxyethylmethyl sulfone (MEMS), lowers the melting
point to 15.degree. C. The subambient melting of the compound
formed by adding the same group to the symmetric dimethyulsulfone
(DMS) (mp=110.degree. C.) yielding methoxymethylmethyl-sulphone
(MMMS), the change in melting point being 90K. Attaching the
methoxy group to one end of the symmetric diethyl sulfone (DES)
gives ethyl methoxy ethyl sulfone (EMES) with an even lower melting
point, 2.degree. C., vs 74.degree. C. for the symmetric compound.
These data, along with data for several other variants, are
summarized in Table 1.
The glass transition temperatures of the new sulfones are described
as follows. For the mono asymmetric sulfones such as EMES, EMEES
(ethyl methoxyethoxyethyl sulfone) and EMEEES (ethyl
methoxyethoxyethoxyethyl sulfone), the glass transition temperature
increases with increasing ether chain length, see Table 1, implying
that the increasing molecular weight effect offsets the decrease in
T.sub.g expected from the dilution of the cohesive sulfone
groups.
The ionic conductivities, at any temperature, follow the order:
EMS>MEMS>EMES>DMES>EMEES>EMEEES, and appear to
follow the order of the respective sulfone viscosities. Of the
possible synthesized sulfones, the room temperature conductivities
of lithium salt solutions of MEMS and EMES are the highest. Since
the difference is not large, and the ease of synthesis and
purification greater in the case of EMES, the latter is adopted for
making solutions for the electrochemical stability and cell
performance tests.
In FIGS. 4a-4b, the cyclic voltammetry scans from which the
electrochemical windows for 1.0M LiTFSI solutions at Pt working
electrode under the scan rate of 1 mv/s in EMES, EMEES are
obtained. FIG. 4a shows EMES, while FIG. 4b is EMEES. The cyclic
voltammetry scans are well above 5.0v vs. Li.sup.+/Li. FIGS. 4a-4b
also show that, with increasing ether chain length, the
electrochemical stability decreases, from 5.6v for EMES, 5.3v for
EMEES, (vs 5.9v for EMS) showing that stability advantage of
sulfone, as a class of solvent, is diminishing with increasing
ether group concentration.
FIG. 5 shows a test of the ether sulfone-based solutions for
reversible intercalation into the graphite designated MCMB25-28,
for the first three cycles of the cell MCMB25-28|1M
LiPF.sub.6/EMES|Li during cycling at constant current density of
0.013 mA.cm.sup.-2. The corresponding charge and discharge
capacities of the first three cycles are 343.0, (202.8); 251.4,
(200.5); 219.2, (193.0) mAh/g, respectively.
Next, the performance of the new solutions with lithium metal
anodes and Cr.sup.3+-modified LiMn.sub.2O.sub.4 spinel
intercalation cathodes are tested. FIGS. 6a-6b compare the cell
performance using different 1M lithium salts in EMES during the
first cycle under different current densities. FIG. 6a shows data
from the cell using 1M LiTFSI/EMES electrolyte. FIG. 6b shows data
from the cell using 1M LiPF.sub.6/EMES electrolyte. Each cell shows
two well-defined discharge plateaus, around 4.0 and 4.1v versus
Li/Li,.sup.+ respectively. It is also seen that the capacities
decrease with increasing current density.
When the charge/discharge rates are raised, there is progressively
less time for lithium ions to diffuse through the LiMn.sub.2O.sub.4
crystallites. At higher rates, only lithium ions located in the
outer regions of the grains are accessible for reaction, causing a
reduction in capacity. However, comparatively the cell using 1M
LiPF.sub.6 electrolyte exhibited a higher capacity than the cell
using 1M LiTFSI/EMES electrolyte under similar current densities.
In addition it has been shown that the charge/discharge capacities
for the cells using LiTFSI/EMES decreases very quickly with cycling
due to its failure to form effective SEI layers, thus LiPF.sub.6 is
useful as the lithium salt for full cell test. The corresponding
cell performance under the current density of 0.092 mA cm.sup.-2
using 1M LiPF.sub.6/EMES in terms of charge/discharge capacities
and coulomb efficiency is shown in FIG. 7. This cell showed
excellent cyclability, more than 200 cycles, tending to stabilize
after 200 cycles at a discharge capacity around 50 mAh/g and a
stable coulomb efficiency around 0.86.
It is further noted that improved performance may be obtained when
the present hybrid sulfones are mixed with fluorinated sulfones on
the one hand or with alkyl carbonates on the other. The
incorporation of oligoether segments into molecular sulfones lowers
the freezing point to sub-ambient values, without decreasing the
electrochemical window, but may increase the viscosity with
consequent lowering of lithium salt solution conductivities.
However, any decrease in conductivity can be compensated by
fluorination of the R1 and R2 alkyl groups. The
oligoether-containing sulfones retain high electrochemical
stability with "windows" well above 5.0v versus Li.sup.+/Li. It is
possible that Li.sup.+ may be intercalated/de-intercalated into
graphite electrode by using oligoether-containing sulfones.
In another embodiment, the novel non-cyclic, non-symmetrical
sulfones are substituted with perfluoromethyl (trifluoromethyl,
--CF3) or perfluoromethylene (--CF2) groups. Substitution of a
methyl, --CH3, group by a perfluoromethyl, --CF3, is surprisingly
found to advantageously decrease the viscosity of the sulfone,
thereby increasing the conductivity of the electrolyte solutions
and increasing the penetration of the electrolytes into the cathode
and separator in electrolytic cells at ambient conditions.
Useful are the novel fluorinated sulfones CF3CH2SO2CH3
(2,2,2-trifluoroethylmethyl sulfone, CF3MMSF) and CF3CH2CH2SO2CH3
(CF3EMSF). Also available is CF3MMSF which exhibits very high
conductivity, for example, in lithium chlorate solutions. The
fluorinated non-symmetrical, non-cyclic sulfone further offers
superior wetting, penetration and other surfactant properties.
Several embodiments of the present invention are described in the
following examples, which are offered by way of illustration and
not by way of limitation.
In Example 1, involving preparation of methoxyethyl methyl sulfone
(MEMS), 45.6 g thiourea was dissolved in 150 ml water, 28.8 ml
dimethyl sulfate was added and the solution was refluxed for 1
hour. After cooling to room temperature, 48 g NaOH in 75 ml
distilled water was added and the solution was stirred for 1 hour,
then 55 g chloroethyl methyl ether (ClCH.sub.2CH.sub.2OCH.sub.3)
was added dropwise. After addition the solution was slowly heated
to reflux for 10 hours. The upper organic layer was separated to
obtain the methoxyethyl methyl sulfide
(CH.sub.3OCH.sub.2CH.sub.2SCH.sub.3) with a yield of 55%. The
sulfide was set to oxidation with 30wt % H.sub.20.sub.2 in acetic
acid. On completion of oxidation, most of the solvent was removed.
Dilute NaOH aqueous solution was added to neutralize excess acetic
acid. Water was removed by rotary evaporation and the residual
paste was extracted with chloroform at least three times. The
chloroform was combined and dried over anhydrous sodium sulfate.
Finally chloroform was removed and the crude product was distilled
under vacuum at 95-100.degree. C. to obtain the pure product
MEMS.
In Example 2, involving preparation of MEMS, pre-weighed empty
bottle was cooled in dry ice acetone solution and Methane thiol was
slowly charged into the bottle. The net weight of methanethiol was
obtained by the difference before and after weighing as 21.5 g.
71.6 g 25 wt % NaOH aqueous solution was charged into stainless
steel pressure vessel and cooled with ice water. The vessel was
vacuumed and then under stirring methanethiol was slowly charged
into the vessel. The solution was stirred for 1 hr before 38 g
chloroethyl methyl ether (ClCH.sub.2CH.sub.2OCH.sub.3) was added.
The solution was stirred for overnight at room temperature and then
heated to reflux for 10 hrs before the process was stopped. The
solution was cooled and the upper organic layer was separated to
give a yield of 87%. The sulfide was then subjected to oxidation
with 120 g 30 wt % H.sub.2O.sub.2 and 100 ml acetic acid. After
work up as in Example 1 the crude product was distilled under
vacuum and 35 g pure product was isolated with a yield 71%.
In Example 3, involving characterization of MEMS, glass transition
temperature T.sub.g was measured using a DTA instrument. The
heating rate used was 10K/min. T.sub.g was defined as the onset
temperature of the heat capacity jump and T.sub.m was defined as
the temperature at which the melting peak reaches its maximum. The
boiling point was recorded during the distillation process. The
T.sub.g and T.sub.m of MEMS are -89.5.degree. C. and 15.degree. C.
respectively, as shown in Table 1. The boiling point of MEMS is
estimated as 275.degree. C. at atmosphere pressure.
Electrolyte solutions of different salts were prepared by
dissolving calculated amount of lithium salts in MEMS at about
80.degree. C., in the case of LiPF.sub.6 salt the temperature is
controlled around 50.degree. C. The measurement of DC conductivity
was carried out using a frequency impedance analyzer. The
measurements were made automatically during heating of the
pre-cooled samples at 1K/min by means of a programmed controller.
The temperature dependence curve for MEMS containing 1.0M LiTFSI is
shown in FIG. 3. The T.sub.g and room temperature ionic
conductivities of 1.0M different lithium salts in MEMS are shown in
Table 2. In general, Table 2 shows glass transition temperature
(T.sub.g/.degree. C.) and room temperature conductivity
log(.sigma..sub.25/S cm.sup.-1) of 1M different lithium salt
solution in different sulfones.
TABLE-US-00002 TABLE 2 LiTFSI LiSO.sub.3CF.sub.3 LiClO.sub.4
LiBF.sub.4 LiPF.sub.6 LiSCN Sulfone T.sub.g log.sigma..sub.25
T.sub.g log.sigma..sub.25 T.sub.g log.si- gma..sub.25 T.sub.g
log.sigma..sub.25 T.sub.g log.sigma..sub.25 T.sub.g lo-
g.sigma..sub.25 EMS -96.0 -2.27 -103.0 -3.00 -110.0 -2.95 -111.0
-2.80 -86.2 -2.55 -101.5 - -3.35 MEMS -81.0 -2.83 -83.4 -3.00 -88.0
-2.93 -84.0 -3.03 -82.0 -2.91 -86.5 -3.- 15 EMES -83.3 -2.85 -87.5
-3.05 -88.0 -3.10 -85.5 -2.89 -88.7 -2.92 -82.5 -3.- 62 EMEES -73.4
-3.12 -74.0 -3.71 -76.0 -3.39 -76.4 -3.48 -70.4 -3.61 -77.0 -3- .92
EMEEES -71.6 -3.25 -68.6 -3.85 -79.4 -3.50 -78.5 -3.55 -77.0 -3.80
-74.6 -- 3.96 DMES -84.0 -2.99 -83.0 -3.70 -76.4 -3.16 -84.0 -3.30
-82.0 -3.09 -82.5 -3.- 72
In Example 4, involving preparation of ethyl methoxyethyl sulfone
(EMES), 57 g NaOH was dissolved in 57 g H.sub.2O and cooled with
ice water, 88.4 g ethanethiol was added to the solution slowly. The
solution was stirred for half hour before 135 g chloroethyl methyl
ether (ClCH.sub.2CH.sub.2OCH.sub.3) was added. After addition the
solution was stirred at room temperature for several hours before
it was heated to reflux for overnight. The reaction was stopped and
cooled to room temperature. Ethyl methoxyethyl sulfide
(CH.sub.3CH.sub.2SCH.sub.2CH.sub.2OCH.sub.3) in the upper organic
layer was separated, 156 g, yield 91%. 100 g Ethyl methoxyethyl
sulfide was set up for oxidation with 170 g 50 wt % H.sub.2O.sub.2
and 200 ml acetic acid. After work up as in Example 1 the crude
sulfone was distilled and the fraction at 85-88.degree. C. /0.3
Torr is collected.
In Example 5, involving characterization of EMES, the T.sub.g and
T.sub.m of EMES are -91.0.degree. C. and 2.degree. C. respectively,
as shown in Table 1. The boiling point of MEMS is estimated as
286.degree. C. at atmosphere pressure. Salt solutions of EMES were
prepared, as described in Example 3, and their ionic conductivities
were measured using the method described in Example 3. The
temperature dependence curve for EMES containing 1.0M LiTFSI is
shown in FIG. 3. The T.sub.g and room temperature ionic
conductivities of 1.0M of different lithium salts in EMES are shown
in Table 2.
The cyclic voltammogram of 1M LiTFSI/EMES electrolyte is recorded
at 1.0mv/s at a Pt working electrode with lithium as both counter
and reference electrode using a potentiostat/galvanostat
instrument, as shown in FIG. 4a.
In Example 6, involving an electric current-producing device
employing EMES electrolytes, electrochemical half cells, Li ||
sulfone electrolyte || MCMB25-28, and Li || sulfone electrolyte ||
LiCro.sub.0.015Mn.sub.1.985O.sub.4 are constructed using fiber
glass paper as the separator. The cathode solution having 82%
active material, 10% carbon black and 8% PVdF in
N-methylpyrrolindone is cast directly on the pre-weighed stainless
steel electrode. The electrode is dried, first at room temperature
and then at 100.degree. C. under vacuum for two days. The weight of
the electrode is determined inside the dry box, and the weight of
active material obtained by difference. The MCMB25-28 composite
electrodes are made in a similar way from slurry of 90% MCMB25-28
and 10% PVdF in N-methylpyrrolindone.
Test cells were constructed by using Whatman glass fiber filter
soaked in the electrolyte solution of Example 5 as the separator
and a lithium anode and LiCr.sub.0.015Mn.sub.1.985O.sub.4 (or
MCMB25-28) cathode. The tests were all carried out in an
argon-filled glove box. The voltage profile of the charge/discharge
process was monitored using a battery cycler. A constant current
ranging from 0.01.about.0.1 mA/cm.sup.2 were used with pre-set
cut-off voltage of 0.01.about.2.0V for Li|| electrolyte|| MCMB25-28
cell and 3.0.about.4.3V for Li|| electrolyte||
LiCr.sub.0.015Mn.sub.1.985O.sub.4 cell respectively. At these
cut-off voltages a computerized cycler automatically switches the
test cells to charge or discharge. The test results are shown in
FIGS. 5, 6a-b, and 7, respectively.
Another set of experiments are performed using commercial electrode
sheets (synthetic graphite and LiCoO.sub.2). The electrodes are cut
into disc with area of 0.72 cm.sup.2 and assembled either in a half
cell of Li || electrolyte || graphite or full cell of graphite ||
electrolyte || LiCo.sub.0.sub.2. A constant current density of 0.14
mA/cm.sup.2 was used for both charging and discharging with pre-set
cut-off voltage of 0.01.about.2.0V for Li || electrolyte ||
graphite cell and 2.5.about.4.2V for graphite || electrolyte ||
LiCoO.sub.2 cell, respectively. The result is shown in FIGS.
8a-8b.
In Example 7, involving characterization of mixtures of EMES with
carbonates, the mixtures of EMES with carbonates were prepared by
mixing different weight percentage of either ethylene carbonate
(EC) or dimethyl carbonate (DMC) in EMES. 1.0M LiPF.sub.6
electrolyte solution was prepared by dissolving the salt in the
mixtures at about 50.degree. C., as described in Example 3. The
ionic conductivities were measured using the method described in
Example 3 and their temperature dependence curves are shown in
FIGS. 9a-9b. Addition of EC to the electrolyte solution increases
the ionic conductivities in all cases due to the higher dielectric
constant of EC.
The cyclic voltammograms of 1M LiPF.sub.6 in EMES/EC and EMES/DMC
are measured, as described in Example 5, which is shown in FIGS.
10a-10d and 11a-11d, respectively. FIGS. 10a-10d are graphs of
cyclic voltammograms for 1M LiPF6 in different EMES/EC mixtures. A)
5 wt % EC; B) 10 wt % EC; C) 20 wt % EC; D) 30 wt % EC. FIGS.
11a-11d are graphs of cyclic voltammograms for 1M LiPF6 in
different EMES/DMC mixtures.A) 5 wt % DMC; B) 10 wt % DMC; C) 20 wt
% DMC; D) 30 wt % DMC. Note that the electrochemical stability
windows are all higher than 5.2v.
Half cell of Li || electrolyte || graphite or full cell of graphite
|| electrolyte || LiCoO.sub.2 were built using the 1M LiPF.sub.6
electrolytes in EMES/EC and EMES/DMC, as described in Example 6. A
constant current density of 0.14 mA/cm.sup.2 was used for both
charging and discharging with pre-set cut-off voltage of
0.01.about.2.0V for Li || electrolyte || graphite cell and
2.5.about.4.2V for graphite || electrolyte || LiCoO.sub.2 cell,
respectively. The results are shown in FIGS. 12 and 13. There is no
graphite exfoliations observed in all the cases studied under the
charge/discharge current density of 0.14 mA cm.sup.-2.
In Example 8, involving characterization of EMES with additives,
ethylene sulfite (ES) is chosen as an additive and mixed with EMES
at the composition of 5 wt %. 1.0M LiClO.sub.4 electrolyte was
prepared by dissolving the salt in the mixture of EMES/ES at about
80.degree. C., as described in Example 3. The ionic conductivities
were measured using the method described in Example 3 and its
temperature dependence curve shown in FIGS. 9a-9b is higher than
that of 1.0M LiPF.sub.6/EMES solution.
The cyclic voltammograms of 1M LiClO.sub.4 in EMES/ES was measured,
as described in Example 5, which is shown in FIG. 14. The
electrochemical stability is still higher than 5.0v.
Half cell of Li || electrolyte || graphite or full cell of graphite
|| electrolyte LiCoO.sub.2 were built using the 1M LiCl.sub.4
electrolytes in EMES/ES, as described in Example 6. A constant
current density of 0.14 mA/cm.sup.2 was used for both charging and
discharging with pre-set cut-off voltage of 0.01.about.2.0V for Li
|| electrolyte || graphite cell and 2.5.about.4.2V for graphite ||
electrolyte || LiCoO.sub.2 cell, respectively. The results are
shown in FIGS. 12 and 13. Note that there is no graphite
exfoliations observed in this case studied under the
charge/discharge current density of 0.14 mA cm.sup.-2.
In Example 9, involving synthesis of ethyl methoxyethoxyethyl
sulfone (EMEES), 40 g NaOH was dissolved in 40 g H.sub.2O and
cooled with ice water. 62 g ethanethiol was added to the solution
slowly. The solution is stirred for half hour before 138.5 g
chloroethyl methoxyethyl ether
(ClCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.3) was added. After
addition the solution was stirred at room temperature for several
hours before it was heated to reflux for overnight. The reaction
was stopped and cooled to room temperature. Ethyl
methoxyethoxyethyl sulfide
(CH.sub.3CH.sub.2SCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.3) in
the upper organic layer was separated with a yield of 96%. The
resulting compound was oxidized with H.sub.2O.sub.2 and acetic
acid, as described in Example 1, to yield ethy methoxyethoxyethyl
sulfone (EMEES).
In Example 10, involving characterization of ethyl
methoxyethoxyethyl sulfone (EMEES), the T.sub.g of EMEES is
-87.6.degree. C. as shown in Table 1. Salt solutions of EMEES were
prepared, as described in Example 3, and their ionic conductivities
were measured using the method described in Example 3. The
temperature dependence curve for EMEES containing 1.0M LiTFSI is
shown in FIG. 3. The T.sub.g and room temperature ionic
conductivities of 1.0M of different lithium salts in EMEES are
shown in Table 2. The cyclic voltammogram of 1M LiTFSI/EMEES
electrolyte was measured, as described in Example 5, which is shown
in FIG. 4b.
In Example 11, involving synthesis of ethyl
methoxyethoxyethoxyethyl sulfone (EMEEES), 40 g NaOH was dissolved
in 40 g H.sub.2O and cooled with ice water, 62 g ethanethiol was
added to the solution slowly. The solution was stirred for half
hour before 182.5 g chloroethyl methoxyethoxyethyl ether
(ClCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.3) was
added. After addition the solution was stirred at room temperature
for several hours before it was heated to reflux for overnight. The
reaction was stopped and cooled to room temperature. Ethyl
methoxyethoxyethoxyethyl sulfide
(CH.sub.3CH.sub.2SCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.sub.2CH.sub.2OCH.s-
ub.3) in the upper organic layer was separated with a yield of 95%.
The sulfide was further oxidized with H.sub.2O.sub.2 and acetic
acid, as described in Example 1, to obtain the ethyl
methoxyethoxyethoxyethyl sulfone (EMEEES).
In Example 12, involving characterization of ethyl
methoxyethoxyethoxyethyl sulfone (EMEEES), the T.sub.g of EMEEES is
-82.5.degree. C., as shown in Table 1. Salt solutions of EMEEES
were prepared, as described in Example 3, and their ionic
conductivities were measured using the method described in Example
3. The temperature dependence curve for EMEEES containing 1.0M
LiTFSI is shown in FIG. 3. The T.sub.g and room temperature ionic
conductivities of 1.0M of different lithium salts in EMEEES are
shown in Table 2.
In Example 13, involving synthesis of dimethoxyethyl sulfone
(DMES), 50 ml 2-chloroethyl methyl ether, 70 g Na.sub.2S.9H.sub.2O,
17.6 g tetrabutylammonium bromide and 50 ml H.sub.2O were mixed
into a three-neck flask equipped with magnetic stirrer and reflux
condenser, and heated at 70.degree. C. with vigorous stirring. The
reaction was continued for overnight. The organic layer was
separated and dissolved in chloroform, washed with distilled water
several times to remove the ammonium salt and dried over anhydrous
sodium sulfate. Solvent was removed using a rotary evaporator, and
dimethoxyethyl sulfide was obtained with a yield of 63%. The
sulfide was oxidized with H.sub.2O.sub.2 and acetic acid, as
described in Example 1, to obtain the corresponding sulfone,
dimethoxyethylsulfone (DMES).
In Example 14, involving characterization of dimethoxyethyl sulfone
(DMES), the T.sub.g and T.sub.m of DMES are -90.7.degree. C. and
47.0.degree. C., respectively, as shown in Table 1. Salt solutions
of DMES were prepared, as described in Example 3, and their ionic
conductivities were measured using the method described in Example
3. The temperature dependence curve for DMES containing 1.0M LiTFSI
is shown in FIG. 3. The T.sub.g and room temperature ionic
conductivities of 1.0M of different lithium salts in DMES are shown
in Table 2.
Implementations of features described in this specification can be
used to provide high oxidation resistance and high conductivity.
This combination of high oxidation resistance and high conductivity
can be used to provide, among other things, burn-resistant,
combustion-resistant electrolytic cells. Moreover, great attention
has recently been given to the difficulty of producing highly
conductive, flame retardant methods and devices for electric
current generation. When a sulfone as described in this
specification is utilized as a solvent to dissolve inorganic
electrolyte salts of highly oxidation resistant anions such as
ClO.sub.4, CF.sub.3SO.sub.3 (triflate), and in particular,
bis(trifluoromethane sulfonyl) imide(--N(CF.sub.3SO.sub.2).sub.2,
lithium imide), solutions can be obtained to provide both high
oxidation resistance and high ambient temperature conductivity.
This resistance to oxidation inhibits energy producing chemical
reactions such as those that might cause explosion or flame. The
result of this inhibition is the increased stability which can be
important in high energy or high temperature batteries.
While this specification contains many specifics, these should not
be construed as limitations on the scope of an invention that is
claimed or of what may be claimed, but rather as descriptions of
features specific to particular embodiments. Certain features that
are described in this specification in the context of separate
embodiments can also be implemented in combination in a single
embodiment. Conversely, various features that are described in the
context of a single embodiment can also be implemented in multiple
embodiments separately or in any suitable sub-combination.
Moreover, although features may be described above as acting in
certain combinations and even initially claimed as such, one or
more features from a claimed combination can in some cases be
excised from the combination, and the claimed combination may be
directed to a sub-combination or a variation of a sub-combination.
Similarly, while operations are depicted in the drawings in a
particular order, this should not be understood as requiring that
such operations be performed in the particular order shown or in
sequential order, or that all illustrated operations be performed,
to achieve desirable results.
Only a few examples and implementations are disclosed. Variations,
modifications and enhancements to the described examples and
implementations and other implementations may be made based on what
is disclosed.
* * * * *
References